class Solution8 {

    int[] dx = {0,0,1,-1};
    int[] dy = {1,-1,0,0};
    boolean[][] vis;
    int m, n, count;

    public int maxAreaOfIsland(int[][] grid) {
        m = grid.length; n = grid[0].length;
        vis = new boolean[m][n];

        int ret= 0;
        for(int i = 0; i < m; i++){
            for(int j = 0; j < n; j++){
                if(grid[i][j] == 1 && !vis[i][j]){
                    count = 0;
                    dfs(grid, i, j);
                    ret = Math.max(ret, count);
                }
            }
        }
        return ret;       
    }

    public void dfs(int[][] grid, int i, int j){
        vis[i][j] = true;
        count++;

        for(int k = 0; k < 4; k++){
            int x = i + dx[k], y = j + dy[k];
            if(x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == 1 && !vis[x][y]){
                dfs(grid, x, y);
            }
        }
    }
}